Paper-based sensing includes a paper-based diagnostic device comprising a portable biomedical device made of paper, wax, and reagents that can analyze biochemical assays in test fluids such as blood, urine and saliva. The devices are small, lightweight and low-cost and have potential applications as diagnostic devices in healthcare, military and homeland security, to mention a few. One aspect of a security measure is to ensure that only the vendor that issued the device, and/or designated entities, are able to determine or “read” the results of the test from said device.